Barack and Michelle Obama sent a goodwill message to Prince William and bride-to-be Kate Middleton today during an interview about their own private lives.

The US first lady told ABC News William and Ms Middleton looked like best friends.

“Hopefully you will be as happily married as Barack and I,” she said.

During the interview the president and his wife talked at length about their family life and Mr Obama said of his 12 and nine-year-old daughters Malia and Sasha: “They are not watching cable TV. If they have got an option of watching the news or watching SpongeBob, I think it’s pretty clear the choice that they are going to make.”

The girls can’t completely avoid all talk about their father, however. For Malia, he has come up in discussions of current events at school.

“There are issues of the day that come across the conversation. But I have to say that the school is very good about handling it,” Mrs Obama said. “People are very considerate.”

She said Malia had managed to draw a line between her father’s activities and her own.

In the interview, the Obamas offered a glimpse into their life in the most famous house in America.

Their daughters preferred just to be kids, the Obamas said, and avoid listening to the news or reading newspaper headlines. Sasha still wrote letters to Santa Claus and anxiously waited for the Tooth Fairy after she lost a tooth, Mrs Obama said.

The family prays every night before dinner and Mr Obama says it is interesting to hear what his daughters pray for.

“They’ll talk about family and thanking God for blessing us, but they’ll always add a little twist ’I hope we have a great Thanksgiving, I can’t wait to see the cousins’. They used to pray for a dog, until we got a dog.”

“But in the end we always say, ’We hope we live long and strong’,” Mrs Obama added. “Long and strong,” the president echoed.

Asked how he relieves the stress that comes with the world’s top job, Mr Obama said two things that helped the most were exercise and spending time with his children.

Mr Obama said one of the most important things for him in terms of stress reduction “is the fact that if I’m here in Washington, I’m having dinner at 6.30, just about every night and sitting around that table, listening to them, and trying to answer their questions. That keeps my bearings.”

The president said he liked to watch football in the White House Treaty Room, and that he and his wife watched sports news while they work outed in the morning.